Dynamical properties of fluids confined in nanoporous materials exhibit many fascinating phenomena. One such interesting phenomenon is the levitation or floating molecule effect, in which super mobility is attained when the molecular size match closely with pore dimensions. This region of pore size is of wide interest in separation processes, and commonly occurs in carbons as well as other nanoporous materials. Using the oscillator model theory recently developed in the author's laboratory, we demonstrate that the anomalous peak in the diffusivity occurs due to decrease in the frequency in the molecule- host surface collisions, in the region where the solid-fluid interaction undergoes a transition from a double minimum to a single minimum. This effect is however absent at high temperatures. The kinetic energy and the solid-fluid interaction strength are shown to play important roles in determining the occurrence and position of the anomalous peak in the diffusivity, and the transport diffusivity is shown to scale with the factor kBT/åfs based on the oscillator model theory, which is confirmed by simulation. Scaling of transport diffusivities with respect to square root of molecular mass is also observed, which is well established for Fickian diffusion, even in the presence of interactions. The oscillator model theory thus provides a clear physical explanation about the levitation effect and yields valuable insights in to the super-diffusive regime. At high densities the levitation effect is reduced, and high frequency of fluid-fluid collisions in molecularly sized pores leads to an anomalous decrease of diffusivity with increase in density. This effect is adequately explained by the oscillator model using a potential of mean force approach, and will be discussed in detail, combining simulation and theory.